SURFACES TO PAINT - 14325

Electrical contact points and insulators The original enamel, lacquer, or crackle finish on all radio, electrical, and sound equipment, unless existing damage makes refinishing essential Decorative plastic, such as tabletops SURFACES TO PAINT The Navy uses a variety of metal, metal compounds, and synthetic materials to build a ship or boat. Each type of surface requires special preparation and special primers and paint to extend its life cycle. In this section, you will learn about various surfaces and the procedures needed to maintain them properly. Aluminum Surfaces Aboard ship, aluminum surfaces are a special problem. If they’re not treated properly, corrosion results. Corrosion is greater when dissimilar metals (for example, aluminum and steel) are in contact with each other and are exposed to seawater. Seawater is an electrolyte (an electrical conductor). As such, the seawater causes an electrical current to flow between the steel and aluminum surfaces, resulting in galvanic corrosion of the aluminum. The first sign of aluminum corrosion is a white, powdery residue in the area where the two dissimilar metals make contact. Later, the aluminum surface is pitted and scarred. Finally, there is a complete deterioration of the aluminum area. Holes in aluminum plate enlarge and screws, bolts, or rivets pull out, or they may even disintegrate. Before joining aluminum to another metal, give each surface a pretreatment formula and two coats of primer formula. NOTE Never use red lead as a primer on aluminum. If the joint is exposed to the weather, use insulation tape between the two surfaces, and fill the joint with caulking compound. When aluminum is joined to wood, give the wood one coat of phenolic varnish. Replace any missing fasteners (screws, bolts, rivets, and so on) with items of the original type. (NOTE: Replacements of stainless or galvanized steel may be used.) When painted, the best way to prepare the aluminum surface for repainting is to use hand scrapers, hand and power wire brushes, or fine grit sandpaper. Be careful if you use a power sander to Never use scaling hammers on aluminum. prepare the aluminum surface for repainting. NOTE Steel Surfaces When painting a steel surface, preparation of the surface is important. Steel surfaces must be completely free of rust, loose paint, dirt, scale, oil, grease, salt deposits, and moisture before they are painted. Old paint in good condition is an excellent base for repainting. Smooth, thoroughly clean, and dry the surface before applying new paint. In touch-up painting (when only small areas or spots need repainting), remove old paint to the edges of the spot or area until an area of completely intact paint is reached. (NOTE: This area must be free of rust or blisters underneath the paint.) Feather the edges of the remaining paint. When completely reworking an old painted surface, take the old paint down to the bare metal. Then apply a primer before painting. Never leave a base metal surface exposed overnight. Always put on a primer coat before you secure for the day. Fillers Fill holes, dents, and cracks in all surfaces and open-grained woods before they are finished. Putty, wood fillers, and even sawdust mixed with glue can be used on wood. Use epoxy fillers on steel and aluminum surfaces. The method you use varies with the type of filler. Therefore, follow the instructions carefully. Allow all fillers to dry and then sand them smooth before you apply the first finishing coat. Paint and Varnish Removers Paint and varnish removers are most often used on wood surfaces. However, you can use paint and varnish 18-15 Student Notes: